It is known in the art to add a scavenger to a photographic element in order for the scavenger to prevent oxidized developing agent from reacting within the element at an undesired location or at an undesired point in time. In particular, it is undesirable for oxidized developer to diffuse away from the imaging layer in which it formed and into other color records where it can form dye in the wrong layer. In some formats, it can also be undesirable for toe scale and fog considerations to have oxidized developer form dye at early stages of development. Typically, scavengers reduce or eliminate oxidized developers without forming any permanent dyes and do not cause stains nor release fragments that have photographic activity. They are also typically rendered substantially immobile in the element by incorporation of an anti-diffusion group (a ballast) or by attachment to a polymer backbone.
Known scavengers for oxidized developers include ballasted hydroquinone (1,4-dihydroxybenzene) compounds as described in U.S. Pat. Nos. 3,700,453 and 4,732,845; ballasted gallic acid (1,2,3-trihydroxybenzene) compounds as described in U.S. Pat. Nos. 4,474,874; ballasted sulfonamidophenols as described in U.S. Pat. Nos. 4,205,987 and 4,447,523; and ballasted resorcinol (1,3-dihydroxybenzene) compounds as described in U.S. Pat. 3,770,431. Such known materials are insufficient in their activity, requiring high material usage, thus increasing cost, storage and handling concerns as well as requiring thicker layers, thus degrading sharpness through increased scatter path length. In addition, because these known materials are sensitive to oxidative conditions, they are often insufficiently stable upon long term storage. Finally, many of these materials form stains or colored residues during processing.
It is also known to use certain hydrazide compounds as scavengers for oxidized developing agents as described, for example, in U.S. Pat. No. 4,923,787, 4,971,890, 5,147,764, 5,164,288 and 5,230,992 and in Japanese Patent Publication No. 4-238347, published Aug. 26, 1992. However, these hydrazide compounds suffer from many of the same disadvantages and deficiencies as the hydroquinone, gallic acid, sulfonamidophenol and resorcinol compounds. In particular, these hydrazide compounds are especially deficient in regard to activity and long-term storage stability.
Japanese Patent Publication No. 61-248042, published Nov. 5, 1986, describes the use of certain pyrocatechol derivatives to improve raw stock storability of photographic elements. However, these derivatives are not ballasted and do not function as effective scavengers for oxidized developing agent.
U.S. Pat. No. 4,175,968 discloses the use as scavengers for oxidized developing agent of pyrocatechol compounds of the formula: ##STR1##
wherein R.sup.1 is an acyl group and R.sup.2 and R.sup.3 are hydrogen, alkyl, halogen, sulfo or carboxyl. However, such compounds are insufficiently reactive and are associated with excessive levels of red stain.
U.S. Pat. No. 4,252,893 discloses the use as scavengers for oxidized developing agent of pyrocatechol compounds of the formula: ##STR2##
wherein R.sub.1 is alkyl, alkenyl or acyl and R.sub.4 is halogen, alkyl, alkenyl, cycloalkyl, cyano, --SO.sub.2 R.sub.5 or --COR.sub.5 where R.sub.5 is hydrogen, hydroxy, alkyl, alkoxy, cycloalkoxy, aryloxy or amino. Such compounds provide useful results but improved activity and greater stability are desired to facilitate their commercial utilization.
U.S. Pat. No. 4,476,219 discloses the use as scavengers for oxidized developing agent of gallic acid amide derivatives (1,2,3-trihydroxy-5-carbamoylbenzenes) of the formula: ##STR3##
wherein R.sup.1 and R.sup.2 each represents a hydrogen atom, a substituted or unsubstituted aliphatic group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group with the proviso that they are not both hydrogen atoms and the further proviso that they can combine with each other to form a ring. Such gallic acid amide derivatives suffer from the disadvantage that they form colored stains in both Dmin and Dmax areas to a degree that hinders their commercial utilization.
It is an objective of this invention to provide a new class of reactive scavengers for oxidized developer which can be incorporated in a wide range of photographic elements, and especially in color elements to prevent color contamination between layers, to prevent stain and to reduce fog. It is a particular objective of this invention to provide a new class of reactive scavengers that have high activity, that have excellent stability upon long-term storage and that do not leave colored residues after processing.